These Jewish leaders were worried that the crowds
would rally and glorify Jesus as the Messiah and
king of Israel; then the Romans would take over.

"Then gathered the chief priests and the Pharisees
a council, and said, What do we? for this man doeth
many miracles. If we let him thus alone, all men
will believe on him: and the Romans shall come and
take away both our place and nation."
John 11:47-48